48 Journal of Agricultural Research voi. xii. no. 2 



of the fungus seem to make any marked changes in the fundamental 

 cultural characters, as is clearly shown in the various tables when strains 

 from different hosts are compared. There may be minor differences 

 due to the host from which the strain came, but nothing more. 



The comparison of the cultural characters of many species of parasitic 

 fungi has long been recognized as a reliable index to the identity of the 

 fungus under investigation, and there is no reason why the cultural 

 characters of wood-rotting fungi which are just as uniform and depend- 

 able should not be used for identification purposes. 



The writers have purposely avoided going into a discussion of the 

 results of the use of synthetic agars and of other special media, as these 

 will be taken up in a later article. They have presented here the results 

 obtained from agars easily made and apparently of a uniform enough 

 composition for similar cultural characters to appear on different batches 

 of the same agar even when the acidity, alkalinity, and water content 

 vary considerably. Just how great a variation in these factors must 

 occur to produce a decided change in the cultural characters is a problem 

 for future investigation. 



EXAMPLES OF THE DIAGNOSTIC VALUE OF CULTURAL CHARACTERS 

 IN SPECIES DETERMINATION 



In comparing the cultural characters of closely related but really dis- 

 tinct species marked and constant differences in the character of the 

 mycelium will be found on certain corresponding agars in the series of 

 cultures representing the two species, while if the two fungi are really 

 the same species no constant differences of specific rank will be found. 

 The following fungi will illustrate the diagnostic value of the cultural 

 characters in determining the real position of the species. 



